如何在 SQL 中舍入百分比计算？

Question

I want the below percentage calculation to be to 2 decimal places.

 SELECT 
        (SUM(recovered)/SUM(confirmed_cases)*100) AS recovery_rate
    FROM corona 

However, the following does not work:

SELECT 
    ROUND((SUM(recovered)/SUM(confirmed_cases)*100), 2) AS recovery_rate
FROM corona

I suspect this is a data type issue since the ROUND() takes a number as its first argument and I'm guessing my SUM(...) percentage calculation isn't a number.

What's the fix? Also, is there a general percentage function in SQL?

Answer 1

The problem is probably integer division -- but that depends on the database. You don't mention the database or the types of your columns, but 1/2 = 0, not 0.5 in a database such as SQL Server which does integer division

This is easily fixed. Just change 100 to 100.0 :

SELECT ROUND(SUM(recovered) * 100.0 / SUM(confirmed_cases), 2) AS recovery_rate
FROM corona